Propeller synchronizing apparatus



De@ 30, 1947- c. w. cHlLLsoN ETAL v PROPELLER SYNCHRONIZING APPARATUSFiled lay 14, 1941 4 Sheets-Sheet 2 w. VUE

INVENTORS CHAQ/.Es n/.CH/LLJON BY GEOQGE W BQA DK Dec 30, 1947 c. w.cHlLLsoN E-rm. 2,433,432

PROPELLER SYNCHRONIZING APPARATUS Filed May 14, 1941 4 Sheets-Sheet 3Flcf,

7l INVENToRs CHAQLEJ MCH/Luau L BY GEOQGE W. BQAm.

Dw- 30, 1947- y c. w. cHlLLsoN Erm.` 2,433,432

PROPELLER SYNCHRONIZING APPARATUS Filed lay 14, 1941 4 Sheets-Sheet 4mvENToR CHAleLss WCHILLJON L BY yEW. QADY.

A oRNEY Patenad nec. 3o, 1941 '2,433,432

PROPELLER SYNCHRONIZING APPARATUS Charles W. Chillson, Lake Packanack,and George W. Brady, Upper Montclair, N. J., assignors to Curtiss-WrightCorporation, a corporation. of

Delaware Application May 14, 1941, Serial No. 393,400

5 Claims.

1 This invention relates to synchronizers for multiple power plants andis concerned particularly with a system and the necessary mecha` nism bywhich the speed of a plurality of aircraft 2 change in pitch is securedthrough electric motors 20 geared to the blades of the propeller-s in amanner which is well known in the art. The electric power for pitchchange in the several engines may be controlled to uniformity and to 5.propellers is supplied thereto through slip ring synchronism with amaster constant speed moassemblies 2| connected through a conduit l22 totor. a junction box 23 and thence through conduits The invention isexemplified in connection with 24 to contactor assemblies 25, 26, 21,and 28, reelectrically actuated controllable pitch propellers spectivelyprovided for the propellers I5, I5, I1, which form the speed controlmeans for the enand I8. Power for pitch changing is furnished gines.from a battery 29 or other suitable power source. Pitch change in thepropellers changes the en- The master speed control motor is indicatedat gine driven loadif this load is increased, the 30 and this devicedrives portions of the several engine speed is reduced and if this loadis decontactor assemblies in a manner which will creased, engine speedincreases. shortly become apparent. Selective adjustment A particularobject of the invention is to proof the speed of the master motor 3U isafforded vide mechanism by which the speed' of one or through a iiexibledrive unit 3| connected to a more prime movers may be synchronized witha turntable knob 32 on a control panel 33 which master speed control andin this connection, a panel is further provided with switches necessarysingle master speed control may be utilized for to the complete controlof the propellersystem. any number of prime movers. A further objectElectrical connections from the panel 33 are coorof the invention is toprovide a mechanism redinated with those of the electrical units in thesponsive to speeddifferences between the master junction bOX 23. controland the prime mover which will correct Each engine is provided with asmall A. C. althe speed of the prime mover gradually and withg5ternator, these alternators being indicated at 35, out tendency towardhunting. When the control 36, 31, and 38 and their output is carriedthrough system is electrical incharacter, speed control is appropriatewiring in a conduit 40 to the junction secured by energizing the speedcorrecting mechbox 23 and through the conduits 24 to respective anismfor intervals of time which are substan- Contactin' assemblies 25x26.27. and 28. tially proportional to the degree of lack of syn- Fig. 3shows the mechanism of the master moclironism between the master controland the tor 30 while the lefthand box of Fig. 1 shows the prime mover.Other objects of the invention electrical connections thereof. Themaster mocomprise the provision of specic electrical and tor is a D. C.shunt wound device comprising an mechanical devices to assure properfunctioning armature 44 carried in bearings 45 and provided of thesystem, which objects will become apparwith a commutator 46 engaged bybrushes 41. ent in reading the annexed detailed description The shuntfield ,48 for the motor is series conin connection with the drawings, inwhich: nected with a variable resistance 49 connected Fig. l is afunctional wiring diagram of the by a wire 50 to the positive terminalof the batessential devices of the invention; tery 29. The other end ofthe field is connected Fig. 2 is a perspective diagram of a plurality of40 through wires 5I and 52 to the negative pole of aircraft power plantsand their relationship to the batterythe synchronizer mechanism; Agovernor assembly for the motor includes a Fig. 3 is a side elevationpartly broken away Spring 54 secured to the motor shaft which shrine andpartly in section, showing the master speed carries governor weights anda central contact control motor; 4b point 56 engageable with a lixedcontact point 51 Fig- 4 is a side elevation, partly broken away whoseposition may be adjusted COrlCidentally and partly in section, showingone of the conwith variation in the resistor 49 by a mechanism tac/torassembhes; 58 to set the speed at which the master motor is Fig. 5 is anend View of a contacter assembly; t0 operate. The contact point 56 isconnected Fig. 6 is a longitudina1 section through an al- 50 'GhrOugh aSlip ring and brush 59 t0 the lower ternate form of contactor assembly;brush 41 of the motor commutator. while the Fig. 7 is a section on theline 1-1 of Fig. 6; xed contact 51 is connected to the positive D018 andof the battery. The contact points 58 and 51 are Fig. 8 is a fragmentarywiring diagram approshunted by a resistor 60 which bypasses a portionpriate to the contactor assemblies of Figs. 6 55 of the motor armaturepower relieving the conand '7. tact points of the governor of asubstantial por- Referring first to Fig. 2, we show aircraft ention ofthe load which they would otherwise have gine power plants I I, I2, I3,and I4 each of which to break. It will be seen that the contacts 56 andis provided with a controllable pitch propeller -51 of the governor arein series with the motor respectively designated I5, I6, I1, and I8whose 0o armature and when operating, the governor contacts open andclose at a frequency of several hundred cycles per second to pass,through the motor armature, an average amount oi.' current necessary tomaintain the armature at correct speed. If the armature is not operatingat correct speed, the governor contacts 58 and 51 will either ride open,in which case there is inadequate current flow through the armature, orwill ride closed in which case there is continuous D. C. through thearmature. When operating properly, the governor controlled current isinterrupted D. C. which passes through the motor armature. Thischaracteristic is utilized for automatic protection of the controlsystem by an A. C. protective relay 82 associated with the master motor,this relay being responsive in its closure only to the passage ofalternating current to the relay, the latter opening should the currentthereto be D. C. or nil. The switch of the relay makes or breaks themain negative control wire tothe contactor assemblies 25, 26, 21, and28, as will become aD- parent. When this switch is open, the propellersstay in fixed pitch. y

The motor armature is further provided with a permanent magnet 83electromagnetically coupled to a eld 64 to comprise a single phase A. C.generator whose output is delivered to a frequency responsive electrictachometer 85. The speed adjuster mechanism 58 is coupled to the controlcable 3| and the control knob 32 of Fig. 2 for panel control of mastermotor speed.

'I'he righthand end of the motor armature 44 carries a pinion 68 meshedwith idler gears 89 which in turn are meshed with a drive pinion 10 oneach of the contactor assemblies 25, 28, 21, and 28. these assembliesbeing secured to the end face of the master motor 30 in their properrelation to assure mechanical drive through the gears 68, 69, and 10.Since all of the contactor assemblies are identical, one only (25) willbe described and one only is shown in Figs. 4 and 5. The assemblyincludes a rotor 1| direct connected with the pinion 10 and carryingthree slip rings 12 with which are engaged brushes 13 connecting throughthe conduit system of Fig. 2 with the engine driven alternator 35. Therotor 1| comprises a Winding 16 which, as shown, is delta connected tothe slip rings 12. The electromagnetic field produced in the winding 16when the alternator is running at speed, rotates in a direction oppositeto the mechanical rotation of the armature 1| so that, when thealternator and the master motor are in synchronism, the electromagneticfield from the winding 16 stands still. However, any difl ference inrotational speed between the rotor 1| and the electromagnetic field willcause an advance or retreat of the field with respect to the stationarycontactor assembly housing. The rotor 1| is embraced in part by arotatable stator 18 which is electromagnetically linked in the fieldproduced by the winding 18 so that the stator 18 will either liestationary or will rotate clockwise or counterclockwise in response tosynchronism, or to lack of synchronism in either direction between themaster motor and the engine. The stator 18 is carried in bearings 19 anda shaft extension thereon carries a commutator 80 Whose opposed bars, asshown in Fig. 1, are connected together. A brush carrier 8| embraces thecommutator 80 and includes a brush 82 which is connected with thepositive battery terminal, and a directly opposite brush 83 connected`to a contact point 84 on an arm of the carrier which may engage eitherof two spaced contacts 85 or 86 according to the direction of rotationofthe commutator 80. The contact point is connected by a wire 88 to oneend of a propeller relay coil 88, and the contact point 88 is connectedthrough a wire 90 to the end of a propeller relay solenoid 9|. The otherends of the solenoids 89 and 8| are connected together at 92 whence awire 93 leads to a rectifier 94 and thence to the fixed contact 95normally engaged with a movable contact 96 forming the switch of a delayopening interrupter relay Whose solenoid 91 is connected at one end tothe relay armature which carries the contact 96, and also to thenegative pole oi' the battery through a wire 98, the switch of theprotective relay in the master motor and the wire 52. The other end ofthe solenoid 91 of the interrupter relay is connected through a wire 93and a pigtail |00 to the brush 83 of the carrier 8|.

With the circuit arranged as shown in Fig. 1, a bar of the commutator 80is in engagement with the brushes 82, 83 and, hence, current flows fromthe positive side of battery 29 through the brushes 82, 83 and thence byway of connection |00 and conductor 99 to one terminal of the solenoid81. the other terminal of which is connected to the negative side ofbattery 29 by way of the conductor 98, the switch of the protectiverelay in the master motor and the wire 52. As a result, the solenoid 91is energized, the contacts 85 and 96 are opened and it is impossible toenergize either of the windings 89, 9| at this time.

Should rotation of the commutator 80 in a counter-clockwise direction,Fig. 1, be initiated, the brush holder 8| moves therewith until thecontact 84 engages the contact 88 whereupon movement of said brushholder 8| ceases. As rotation of the commutator 80 continues, theaforesaid bar of the commutator 80, which was described as in engagementwith the brushes 82 and 83, becomes disengaged therefrom and moves intoa dead space whereupon the described cirn cuit through the solenoid 91is opened with resultant closure of the switch 95, 98. As soon as thenext succeeding bar of the commutator l0 comes into engagement with thebrushes 82 and 83, the circuits through the solenoid 91 and the winding9| are closed. The solenoid 91 is of the delay-opening type and, hence,a short interval of time elapses before the contacts 95 and 98 open toopen the circuit through the winding 9|. The propeller relay isconstructed with a delay opening characteristic so that a switch |0|thereof which has been closed by propeller relay energization willremain closed for a finite time interval of the order of a tenth of asecond which is a sufcient time interval to energize the propeller pitchmotor 20 to afford a small change in propeller pitch in the directionappropriate to bring engine speed into synchronism with the mastermotor. The propeller relay also includes a power switch |02 which isclosed in the same manner as above described when the solenoid 89 isenergized. The switches |0| and |82 are connected on one side to lthepositive battery terminal through a heavy conductor |03. The other sideof the switch l0| is connected by a heavy conductor |04 to one of theslip rings in the assembly 2| while the other side of the switch 02 isconnected by a heavy conductor |05 to another of the slip rings of theassembly 2 I. The third slip ring in the assembly 2| is connected by aheavy conductor |08 to the negative terminal of the battery.

In case the conditions should be such that the commutator 80 is rotatingat relatively high speed,

The rotor includes windings Maanen succeeding bars thereof engage andrecede from the brushes 82, 03 with such rapidity that the contacts 95and 96 do not open, this non-opening characteristic of said contacts 95and 96 arising by reason of the fact that the solenoid 91 is of thedelay opening type. Obviously, at this time, the propeller pitch motor20 remains energized to effect a large change in propeller pitch.

The propeller relay solenoids 89 and 9| are shunted by resistors |08 and|09 respectively, which aiord the delay opening characteristic for therelay. A condenser ||0, connected from the return lead 93 of thepropeller relay solenoids to the wire 99, shunts either propellersolenoid which may be in operation, this condenser serving to smooth outenergy supplied to the propeller relays when the commutatorinterruptions are at high frequency due to a. large orf-speed condition.The rectifier 94 under similar off-speed conditions serves to prevent asimilar-smoothing out of the energy supply to the interrupter relaysolenoid, so that this solenoid receives only high frequency impulseswhich are insufficient to operate it.

By the structure above described, energization of the propeller pitchchanging motor is made for constant length intervals, the intervalsoccurring at a frequency proportional t0 the speed of rotation of thecommutator 80. If the speed of rotation of the commutator 80 issubstantial, these constant length intervals will overlap so that thepropeller relay is held in engagement and continuous current is suppliedto the propeller pitch motor. If the speed of rotation of the commutator80 is low, only occasional jogs of electrical energy will be transmittedto the propeller pitch motor to afford gradual' correction of propellerpitch to attain engine synchronism with the master motor whensynchronism is almost exact. In other words, the average amount ofcurrent supplied to the propeller' pitch motor to correct the speedcondition is, in general, proportional to the extent of the oii-speedcondition between the en gine and the master motor.

In Figs. 5, 7, and 8, we show an alternate arrangement of contacterassembly designated as H5. This device includes a rotor H6 carried inbearings i il and i ld and driven through a pinion ||9 from the mastermotor previously described. |20 connected through slip rings itl andbrushes |32 to the engine alternator 35, and, in the manner similar tothat previously described, the electromagnetic field produced by thewindings |20 is stationary when engine speed and master motor speed aresynchronous. The field drifts rotationally to right or left as an offsynchronism condition exists. A squirrel cage type stator y|24 lies inthe electromagnetic field and is borne by the housing of the assembly inbearings |25, the stator shaft |26 being oscillatable against acentering spring |21 and being displaced to right or left, as shown inFig. '1, in accordance with the torque resulting from slip between theelectromagnetic fleld and the stator |24. The shaft |26 carries asubstantially spiral cam |29 which forms a switch Contact connected tothe positive battery terminal by a wire |30. Mounted in the housing is aradially reciprocable contact carrier |32 having anupper contact |33engageable at times with the upper surface of the contact |29 andcarrying a lower contact |34 engageable at times with the lower surfaceof the contact |29. The contacts |33 and |34 are connected by suitableconductors to the propeller slip ring assembly 2| and thence to thepropeller pitch changing motor.

Closure ci' the contacts |29 and |33 will serve to change propellerpitch in one sense while closure of the contacts |29l and |34 will serveto change propeller pitch in the 'other sense. The carrier |32 iscontinually reciprocated by a cam |36 which engages a roller |31journalled in the carrier, the cam |36 being carried on shaft |38 whichis rotated continually by the master motor through gearing |40. Thecontacts |33 and |34 are yieldably mounted so that, as the carrier |32is reciprocated when the cam contact |29 is ofi center, kcontact ofvarying dwell but at constant frequency will be made between the element|29 and either of the contacts |33 or |34. The element |29 includes endabutments |42 engageable with the reciprocating contact points toprevent movement of the element |29 beyond established limits. The slopeof the element |29 is so arranged that it will make continued contactwith one of the points |33 or |34, despite reciprocation of the carrier|32, when the element |29 is at either extreme position. This willprovide for continuous energization of the propeller pitch changingmotor when the oi speed condition between the engine and the mastermotor is great. As the off speed condition diminishes, interruptedcontacts are established to bring propeller pitch gradually to theposition for engine synchronism. As in the iirst embodiment, the averagecurrent supply to the propeller pitch changing motor will be generallyproportional to the amount of off speed between the engine and mastermotor.

The principal difference in the second embodiment is that interruptedcurrent jogs to the propeller pitch motor are made at constant frequencyand varying'dwell whereas, in the iirst embodiment, the jogs were givenat varying frequency and constant dwell.

In the appended claims, the references to proportional or itsderivatives shall be understood as generically describing intermittentenergization, varying in accordance with the extent of theofi-synchronism condition, of the speed changing means recited whethercaused by variation in duration of energy applications thereto or byvariation in frequency of energy applicationsk thereto.

While We have described our invention in de 'l tail in its presentpreferred embodiment, it will be obvious to those skilled in theart,'after under standing our invention, that various changes andmodifications may be made therein without departing from the spirit orscope thereof. lWe aim in the appended claims to cover all suchmodifications and changes.

We claim as our invention:

1.1In an engine speed control system, a con stant speed datum, a membercontrolled by the datum and the engine to rotate at a speed proportionalto the speed difference between said datum and engine, an engine speedcontrolling electric motor, a control circuit therefor, an interrupterin said circuit actuated by, and at a reJ qucncyproportional to thespeed of said mernm ber, a delay opening relay whose solenoid is in saidcontrol circuit, and an operating circuit for the speed controllingelectric motor controlled in its opening and closing by said relay, thedelay time dwell of said relay being greater than the cyclic interval ofsaid interrupter when said member is rotating at more than a certainspeed of rotation.

2. In an engine speed control system, a, constant speed datum, a membercontrolled by the datum and the engine .to rotate at a speed prowlportional to the speed difference between said datum and engine, anengine speed controlling electric motor, a control circuit therefor, aninterrupter in said circuit actuated by. and at a frequency proportionalto the speed of said member, a delay opening relay whose solenoid is insaid control circuit, and an operating circuit for thespeed controllingelectric motor controlled in its opening and closing by said relaywhereby, when the cyclic interval of said interrupter is greater thanthe relay delay, said electric motor will be energized for periods ofconstant dwell said periods being at a frequency proportional t thespeed difference between the datum and the engine, and, when the cyclicinterval of said interrupter is less than the relay delay, said relaywill effect continuous energization of the speed controlling electrlcmotor.

3. In an engine speed control system, a constant speed datum, a membercontrolled by the datum and the engine to rotate at a speed proportionalto the speed difference between said datum and engine, an engine speedcontrolling electric motor, a control circuit therefor, an interrupterin said vcircuit actuated by, and at a frequency proportional to thespeed of said member, a delay opening relay whose solenoid is in saidcontrol circuit, and an operating circuit for the speed controllingelectric motor controlled in its opening and closing by said relaywhereby said electric motor will be energized continuously or forconstant intervals of varying frequency accordingly as the interrupterfrequency is greater or less than the relay delay.

4. In an engine speed control system, an electrically operated enginespeed controller, an operating circuit therefor, a constant speed motorhaving a Wound rotor, an engine driven alternator whose output frequencyis proportional to engine speed and which output is fed to said rotor toproduce an electromagnetic field rotatable in the direction and speedaccording to the direction and degree of off-speed between the engineand constant speed motor, an oscillatable stator linked with said fieldand movable thereby, a member carried by said stator including selectiveswitch means to energize said engine speed controller operating circuit,and an interrupter in said circuit having a frequency of make-andbreakproportional to the oispeed condition between the engine speed and theconstant speed motor speed.

5. In an engine speed control system, an electrically operated enginespeed controller, an operating circuit therefor, a constant speed motorhaving a wound rotor, an engine driven alternator Whose output frequencyis proportional to engine speed and which output is fed to said rotor toproduce an electromagnetic field rotatable in the direction and speedaccording to the direction and degree of off-speed between the engineand constant speed motor, an oscillatable stator linked with said fieldand movable thereby, a member carried by said stator including selectiveswitch means to energize said engine speed controller operating circuit,and an interrupter in said circuit having a dwell of circuit closureproportional to a function of the off-speed condition between the enginespeed and the constant speed motor speed.

CHARLES W. CHILLSON. GEORGE W. BRADY- REFERENCES CITED The followingreferences are of record in the iile of this patent:

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